Quote:
Originally Posted by Hendog
Hey Rick, the current flowing through R1 (fan or coil) also flows through the drain. Does it matter then if R1 is on the source leg or drain leg?
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Remember what turns it on is voltage from the gate to the source to get carriers in the channel.
For example if you put 3 volts on the gate referenced to ground and there is something in the source leg that raises the source voltage above ground.... Vgs goes down.
The other thing is you really need to add some hysteresis in the circuit to make sure that the mosfet is not in the active region very long or it sits and oscillates.